Description

Model 2253 is a compact and robust USB-compatible audio/video codec that is powered from a single USB port. Its small size (1.5" x 2.75") and low power consumption (1.5 Watts) make it ideal for both portable and embedded applications.

Simplified 2253 block diagram

Multiple, independent video processors allow the unit to simultaneously produce two different video streams from its single composite input and send the streams out over USB. One of the streams can be a low-latency uncompressed stream (useful for real time previewing) and the other compressed, or both streams may be compressed. Image transformations (resolution, rotation, mirroring) are independently configurable for each stream, as well as compression type and bit rate in the case of compressed streams.

Pause and resume are supported for both stream capture and playback. Up to 1024 bytes of application-supplied data can be inserted in the H.264 or MPEG stream at regular frame intervals or single shot, and closed captions are supported for H.264 streams.

Stream Formats

Video and audio are available as elementary streams or may be multiplexed in MP4 container format.

The 2253 supports transport streams by packaging elementary streams with error correction and stream synchronization to help maintain integrity when the signal is degraded. The transport stream uses AAC audio and H.264 for MPEG-4.

Digital I/O

One general purpose digital input and one output are provided. The output is optically isolated, while the input may be either optically isolated or galvanically coupled. The input is sampled every millisecond and, when a state change is detected, a notification is sent to the application program. The input can also be used to control the flow of any stream, without host involvement.

Audio Sync

Real-Time Text Overlay

The overlay generators can position up to 160 characters of text anywhere in the video frame. A unique text string, consisting of mixed constant and variable text, may be defined for each overlay generator. Text variables are automatically updated every video frame. Supported variables include time, date, and frame count.

Graphics Overlay with Unicode Text

Overlay images and high quality, styled unicode text (bold, italic, underline, outline and shadow) can be displayed on top of the composite video output, compressed streams, or preview stream (but not low latency preview stream).

Up to 256 full-color overlay regions are supported on the composite output, and up to eight monochrome-only regions are supported on compressed and preview streams (except low latency preview). BMP and PNG image formats are supported, with 24 or 32 bits per pixel and up to eight transparancy levels.

Please note that preview/compressed stream overlays (text or graphics) modify luminance only and consequently may be tinted by background colors. Also, unlike composite output overlays, these overlays are limited in number, size and complexity; see the above right image for an example what is possible.

Video Decoder

The 2253 can also perform as a decoder, converting a USB-supplied compressed audio/video stream into standard analog video and audio signals. (Note: Decoding is guaranteed only for streams captured with the 2253). The following formats are supported for decoding: MPEG-4, H.264, MP4 and MJPEG. The composite output video can be sourced from either the composite video input or a decoded compressed stream.

Low Latency Preview

Model 2253 supports a low latency preview mode for real-time applications. When capturing in native resolution (704x480 for NTSC or 704x576 for PAL) this mode reduces the overall latency by approximately one frame time. See the latency timing diagram for details.

Cables

A USB cable is supplied with model 2253. Video cables must be purchased separately.

Packaging Options

Model 2253 is a small footprint, bare-board version for OEM applications.It is CE compliant when used in an appropriate enclosure.